Recast is a navigation mesh generation library and Detour is a path-finding library.

Detour takes the poly soup created by Recast and performs A* searches from any two points on the navigation mesh. The result is a list of points that compose the path to take.

Typically if you need a lot similar paths for agents all moving in the same direction a gradient dissent map is cheaper and can be computed offline. Agents could then do corrective path-finding queries if they get blocked.